Personal care products are absorbent articles including diapers, training pants, feminine hygiene products such as sanitary napkins, incontinence devices and the like. These products are designed to absorb and contain body exudates and are generally single-use or disposable items which are discarded after a relatively short period of use—usually a period of hours—and are not intended to be washed and reused. Such products usually are placed against or in proximity to the wearer's body to absorb and contain various exudates discharged from the body. All of these products typically include a liquid permeable bodyside liner or cover, a liquid impermeable outer cover or backsheet, and an absorbent structure disposed between the bodyside liner and outer cover. The absorbent structure may include a surge layer subjacent to and in liquid communicating contact with the bodyside liner, and an absorbent core often formed of a blend or mixture cellulosic pulp fluff fibers and absorbent gelling particles subjacent to and in liquid communicating contact with the surge layer.
Desirably, personal care absorbent articles exhibit low leakage from the product and a dry feel for the wearer. It has been found that urination can occur at rates as high as 15 to 20 milliliters per second and at velocities as high as 280 centimeters per second and that an absorbent garment, such as a diaper, may fail by leaking from the leg or front or back waist areas. The inability of the absorbent product to rapidly uptake liquid can also result in excessive pooling of liquid on the body-facing surface of the bodyside liner before the liquid is taken up by the absorbent structure. Such pooled liquid can wet the wearer's skin and can leak from leg or waist openings of the absorbent article, causing discomfort, potential skin health problems, as well as soiling of the outer clothing or bedding of the wearer.
Leakage and pooling can result from a variety of performance deficiencies in the design of the product, or individual materials within the product. One cause of such problems is an insufficient rate of liquid intake into the absorbent core, which functions to absorb and retain body exudates. The liquid intake of a given absorbent product, therefore, and particularly the bodyside liner and surge materials used in absorbent product, must attempt to meet or exceed the expected liquid delivery rates into the absorbent product. An insufficient intake rate becomes even more detrimental to product performance on second, third, or fourth liquid surges. In addition, leakage may occur due to poor wet product fit that results when multiple insults are stored in the target location and cause sagging and drooping from the wet, heavy retention material structure.
Various approaches have been taken to reduce or eliminate leakage from personal care absorbent articles. For example, physical barriers, such as elasticized leg openings and elasticized containment flaps, have been incorporated into such absorbent products. The amount and configuration of absorbent material in the zone of the absorbent structure in which liquid surges typically occur (sometimes referred to as a target zone) also have been modified.
Other approaches to improving overall liquid intake of absorbent articles have focused on the bodyside liner and its capacity to rapidly pass liquid to the absorbent structure of the absorbent article. Nonwoven materials, including bonded carded webs and spunbond webs, have been widely used as bodyside liners. Such nonwoven materials generally are intended to be sufficiently open and/or porous to allow liquid to pass through rapidly, while also functioning to keep the wearer's skin separate from the wetted absorbent underlying the liner. Attempts to improve the liquid intake of liner materials have included, for example, aperturing the liner material, treating the fibers forming the liner material with surfactants to enhance the wettability of the liner, and altering the durability of such surfactants.
Yet another approach has been to introduce one or more additional layers of material, typically between the bodyside liner and absorbent core, to enhance the liquid intake performance of the absorbent product and to provide separation between the absorbent core and the bodyside liner adjacent the wearer's skin. One such additional layer, commonly referred to as a surge layer, can suitably be formed of thick, lofty nonwoven materials. Surge layers, particularly high loft, high bulk, compression resistant fibrous structures, provide a temporary retention or absorption function for liquid not yet absorbed into the absorbent core, which tends to reduce fluid flowback or wetback from the absorbent core to the liner.
Despite these improvements, the need exists for further improvement in the liquid intake performance of liner materials employed in absorbent articles. In particular, there is a need for liner materials that can rapidly intake and then control the spreading of a liquid insult to the underlying layers. This improved handling is critical for narrow crotch absorbent product designs that utilize less retention storage material in the target region and incorporate distribution features that remove fluid for storage in remote locations in order to alleviate fit problems as a means to reduce leakage. The present invention provides a heterogeneous surge material that provides for such improved liquid intake and controlled spreading when used in absorbent articles.